Abstract

In this paper, a compact dual band rat race coupler is proposed at two different frequency bands. The dual band property is accomplished by transforming the length and impedance of conventional quarter wave transmission line into dual band T shaped sections. To achieve the compactness, the dual band rat race coupler was transformed into fractal structure using sierpinski curve analogy. Simple design equations are used for basic design geometries. Then the rat race coupler geometries are analyzed using CST studio and then realized at 0.9425 and 1.96 GHz for global system of mobile communications (GSM) bands. Excellent agreement between simulated and measured results demonstrates the performance of the proposed couplers.